The invention relates to a method for evaluating a movement pattern that is recorded using a number of markers moving together with the body of a subject. It relates further to a corresponding apparatus for carrying out the method. In this context, movement pattern is understood to mean the pattern of the head and trunk movement (cranio-corpo-gram).
Balance dysfunctions occur as a main or consequential phenomenon of a multiplicity of pathological findings. In the first instance, these are constitutional phenomena, such as vertigo, or damage caused during an accident, e.g. whiplash. In the second instance, numerous clinical pictures are linked to reversible or irreversible balance control disorders, also including psychosomatic illnesses, such as schizophrenia, dementia, depression and Parkinson""s syndrome. Particularly when a person is standing up, keeping one""s balance requires a highly complicated control mechanism that involves not only the organ of balance (vestibular apparatus) situated in the inner ear but also, in particular, the eyes and ears as well as touch receptors and various regions of the brain. The so-called xe2x80x9ccranio-corpo-graphyxe2x80x9d method of examination used for diagnosis purposes leads to the realization that disorders in various regions of the organs involved in balance control produce a particular characteristic movement pattern in a subject to be examined. By observing the movement pattern, cranio-corpo-graphy can be used to locate the disorder empirically within the balance control system. This in turn allows conclusions to be drawn about the illness causing the balance dysfunction.
On the basis of the device disclosed in the document xe2x80x9cForschungsbericht Cranio-Corpo-Graphie (CCG) [Cranio-corpo-graphy (CCG) Research Report]xe2x80x9d, ISBN 3-88383-126-3 (June 1986), which appeared in the documentary series of the Hauptverband der gewerblichen Berufsgenossenschaften e.V. [Main association of the registered organization of professional business associations], the head and trunk movement of a subject is made visible using markers in the form of incandescent lamps. A respective lamp is positioned on each of the subject""s two shoulders, one is positioned above his/her forehead and one is positioned at the back of his/her head. The movement of each marker in the horizontal plane is recorded photographically by a camera configured above the subject under continuous exposure as a luminous trace in a so-called cranio-corpo-gram. The luminous traces are evaluated manually on the photograph after the experiment has been carried out.
However, manual evaluation of the recordings, which is done either by measuring the geometry of the luminous traces or by associatively linking the complex movement pattern to comparison patterns, termed xe2x80x9cgraphical elementxe2x80x9d, is associated with a considerable time requirement. Furthermore, a fundamental disadvantage is that some of the information produced in the experiment is lost during photographic recording of the marker movement. Thus, the photograph shows only the horizontal components of the marker movement. It is thus not possible to make any statements about vertical movements and the absolute height of a marker in space. Complex calibration of the photograph is therefore necessary in order to be able to compare cranio-corpo-grams for subjects of different heights. Since the luminous traces of all the markers are contained in a single photograph, there is often masking due to the luminous traces overlapping, which makes it more difficult, or even impossible, to characterize an individual luminous trace. Information is also lost in the blind angle, which is situated directly below the camera and in which the camera projects into the path of rays running between the mirror and a marker.
DE 38 29 885 C2 discloses a device in which, instead of a camera, a configuration of photoelectric cells positioned above the subject is used for recording the luminous traces. This configuration eliminates the blind angle. In this case, the luminous traces are analyzed using a digital computer for calculating the movement deviations relevant to cranio-corpo-graphy. However, this does not provide for evaluation in terms of interpreting recorded movement patterns.
It is accordingly an object of the invention to provide a method and a device for evaluating movement patterns recorded using a number of markers moving together with the body of a subject, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known methods and devices of this general type in such a way that the movement pattern can be evaluated while maintaining a particularly high information density and without taking up a lot of time.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for evaluating a head and trunk movement pattern of a subject that includes configuring a plurality of markers to move together with the body of a subject. For each of the plurality of markers, a locus curve in three-dimensional space is detected as a function of time and the locus curve is stored as a data field of a measured data record that is common to the plurality of markers. The movement pattern of the body of the subject is characterized using characteristic variables derived from the measured data record. Reference variables are derived from a stored plurality of reference data records. Each of the characteristic variables is compared with the reference variables derived from the stored reference data records. Each of the characteristic variables is derived from a projection the locus curve of at least one of the plurality of markers onto one of the three datum planes of a Cartesian coordinate system.
In this case, the locus curve for each marker is recorded in three-dimensional space with temporal resolution and is stored as a data field of a data record which is common to all markers. The locus curves representing the movement pattern are then characterized by means of a data processing system using characteristic variables derived from the data record. Each characteristic variable is subsequently compared with reference variables derived accordingly from a stored reference data record, in the style of pattern recognition. To this end, the or each reference variable is ascertained, in a reference measurement, as a characteristic variable of a reference movement pattern. In this context, characteristic variable and reference variable are understood to mean any information which can be derived from the locus curves in order to characterize the movement pattern with regard to pattern recognition.
In this regard, the invention sets out from the consideration that more or less prediagnostic statements that can be derived from a cranio-corpo-gram are based on empirically obtained experimental values. Reliable diagnosis of a clinical picture on the basis of an observed movement pattern therefore requires a multiplicity of reference examinations, because individual properties that are also contained in the movement pattern need to be isolated from pathological properties. The amount of data needed to be processed for statistical validation of the findings becomes so complex that reliable statements are possible only when a lot of time is involved. However, time-consuming evaluation of an examination makes any use in the clinical field unprofitable. Furthermore, it is desirable to keep the loss of information when recording an experiment as low as possible, especially since new findings frequently necessitate renewed evaluation of old examinations or experiments from a new standpoint. Automatic pattern recognition using a computer or a data processing system can result in a particularly detailed analysis of a movement pattern, resulting in standardization of movement forms. It is acknowledged that this result can already contain a probability statement for later diagnosis.
As a result of the three-dimensional recording with temporal resolution, the data record contains all the information from the experiment. In particular, the locus curves for the markers can always be evaluated in isolation from one another. Furthermore, the time profile of the movement pattern is particularly easy to analyze. Modern data processing systems significantly reduce the time required for evaluation as compared with that for manual evaluation of the movement pattern.
The characteristic variables are derived from a projection of at least one locus curve onto one of the datum planes of a Cartesian coordinate system. In comparison with a method disclosed in WO 91/15148 for determining the movement of the cervical spine using three-dimensional representations that are ascertained from three-dimensional image information for a head movement, the locus curve can be displayed, e.g. on a screen, particularly clearly in a two-dimensional projection and can be evaluated efficiently. This is particularly advantageous since the evaluation result used for diagnostic or prediagnostic purposes should be comprehensible for each method step.
Typically, the movement pattern observed in a cranio-corpo-gram shows a periodic structure caused by any body sway in the subject. In a so-called stepping test (based on Unterberger/Fukuda), in which the subject makes stepping movements, half a sway cycle is equivalent to one step by the subject. To derive characteristic variables which give a particularly detailed description of the movement pattern, it is expedient to subdivide the locus curve into sequences on the basis of its periodicity. Particular characteristic variables are therefore ascertained from an individual sequence. Such characteristic variables are, by way of example, the amplitude, the sway duration and the distance covered transversely with respect to the direction of sway (step length).
Since it is acknowledged that the periodicity possessed by any body sway has no exact periodicity in the mathematical sense, the individual sequences are not identical, but only similar. Expediently, in addition or as an alternative to a characteristic variable ascertained from an individual sequence (xe2x80x9csingle-stepxe2x80x9d analysis), an appropriate characteristic variable is therefore ascertained from a number of sequences and is indicated statistically in the form of a mean with its standard deviation. This allows statements to be inferred about the regularity of any body sway.
Quantitative indications regarding the regularity of any body sway are expediently obtained by ascertaining the amplitude distribution and/or the frequency distribution of at least one locus curve. Thus, in particular, the frequency distribution is derived as a characteristic variable from the data record by means of a spectral analysis method, e.g. using so-called xe2x80x9cFast Fourier Transformationxe2x80x9d.
The movement of the body""s center of gravity is ascertained in the form of further expedient characteristic variables. To this end, the distance between the starting position and the finishing position of the respective marker is calculated from the or from each data field of the data record. This can be used to determine the angle of deflection of the body, for example. In addition, characteristic variables ascertained using the mutually relative positions of the markers are used, where the characteristic variables represent the orientation of the body parts in space and their position, particularly that of the head and shoulders, relative to one another. These characteristic variables are, in particular, the intrinsic body spin and the torticollis angle, i.e. the movement of the head with respect to the shoulders. In addition, the length of the or of each locus curve, and hence the total distance covered by the respective marker, can be ascertained as a characteristic variable.
Using a pattern comparison of patterns derived from current data records and from stored reference data records, where the patterns are in the form of graphical elements, the particular degree of correspondence can be determined simply and effectively, using (neuro) fuzzy logic or a neural network. The appropriate graphical elements and/or other characteristic variables can be organized in terms of differential diagnosis. The reference data records are expediently supplemented by the particular current data record, in the manner of a self-learning knowledge base. In this instance, an identifier (associated with each reference data record) for a corresponding clinical picture or pattern allows the corresponding measurement to be evaluated for later diagnosis. Furthermore, an identifier additionally ascertained using the respective correspondence of the data record to a plurality of reference data records enables a probability statement regarding each of a plurality of prediagnosed clinical pictures to be made.
With the foregoing and other objects in view there is also provided, in accordance with the invention, an apparatus for performing the method. The apparatus includes the plurality of markers for attachment to a head and a trunk of the body of the subject during the configuration step. A data processing system is connected to a receiver configuration for recording the locus curve for each marker. The data processing system has a processing stage for calculating a data record that represents the locus curve from signals obtained from the receiver configuration. The receiver configuration can be a number of ultrasonic transceivers, CCD cameras (video cameras), photoelectric elements or the like, configured with a spatial distribution relative to one another, for recording and possibly preprocessing acoustic or optical signals. The corresponding receivers are expediently configured at right angles with respect to one another, so that the markers"" locus curves are recorded in at least two different planes, e.g. the xy plane and the yz plane or xz plane. The coordinate data of the locus curve for the third plane can then be calculated from the measured data from the two receivers. When ultrasound is used instead of light for marking purposes, the measurement can also be carried out in an undarkened room.
A database configured downstream of the processing stage is used for storing reference data records which have preferably been ascertained in a multiplicity of reference measurements. An analysis module or analysis stage in the data processing system uses the currently recorded data record and the corresponding reference data record to ascertain a number of characteristic variables and reference variables. A comparison module or comparison stage ascertains the degree of correspondence between the data records on the basis of the characteristic and reference variables, using pattern recognition, for example. The data processing system subsequently associates with each data record an identifier based on a clinical picture, and uses the identifier to transfer the data record to the database for the purpose of expanding the appropriate reference data record.
The processing stage associates the locus curve for each marker with the data record, expediently as a data field. This produces a matrix containing a number of data fields which corresponds to the number of markers, each data field containing the three spatial coordinates based on a Cartesian coordinate system at the respective instant. The processing stage advantageously has a temporary data record store for temporarily storing the recorded measured data configured downstream of it.
The advantages obtained with the invention are, in particular, that computer-assisted evaluation of the measured data ascertained for a multiplicity of optically or acoustically recorded movement patterns, and the interpretation of curve profiles and function patterns derived therefrom using appropriate characteristic variables, enable a statement to be made about the clinical picture of a disorder forming the basis of the respective movement pattern. This statement can be used for diagnosis. While measured data is recorded on the subject""s body virtually without contact, evaluation takes place in a data processing system which is detached from the subject""s body and in which the measured data is processed and prepared for pattern recognition outside the body.
The evaluation of, in particular, typical clinical pictures showing head/body movement patterns for both ordinary subjects and striking subjects allows a knowledge base to be created containing a multiplicity of reference data and patterns. This knowledge base can be used to associate currently recorded and undiagnosed movement patterns with known clinical pictures. This allows qualitative and quantitative statements to be made, in particular, about psychological, psychosomatic, and/or neurological disorders, such as schizophrenia, depression, and Parkinson""s syndrome, on the basis of the evaluation of the ascertained characteristic variables.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and apparatus for evaluating a movement pattern, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.